Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof;

FIG. 5 is the fifth image thereof;

FIG. 6 is the sixth image thereof;

FIG. 7 is the seventh image thereof;

FIG. 8 is the eighth image thereof; and,

FIG. 9 is the ninth image thereof.

The broken lines showing of the display screen or portion thereof are for environmental purposes only and form no part of the claimed design.

The appearance of the image sequentially transitions between the images shown in FIGS. 1-9. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 